How to troubleshoot a BN44-00424A

[budm]

Re: How to troubleshoot a BN44-00424A

"The GND pin 10 /9 has "Vamp" in the 4th column to the right on the pcb"
The even column pin 10 is 'GND', the ODD column pin 9 is 'VAMP' so no way you can have 18.9VDC on pin 10 GND.
Same for BL-ON, no way you can have 18.9V on that pin, etc.
Vamp reading of about 17~19VDC is fine, it is not tightly regulated power supply for the Amplifier circuit.

After looking at your reports, I see why your report is not right, I was looking at your chart as the STBY column as the EVEN column, and the PWR ON as the ODD column, but no matter since the GND pin 10 shows 18.9V which cannot be right any way.
You have standby column and ON column, you need the EVEN number column whne it is in standby and when TV is ON column, same for the ODD number column, so the readout will have FOUR columns total.

[Vista20]

Re: How to troubleshoot a BN44-00424A

Budm,
I was taking those numbers from the photo I posted much earlier. So, I must be misunderstanding what they printed on the board, or what they printed on the board is in error. Please take another look at the photo of the PCB I posted earlier and let me know if I'm misunderstanding what is printed there.

Looking at the photo of the pin header, I only see pins by the ODD numbers, the pins where the EVEN would be are missing.

[Vista20]

Re: How to troubleshoot a BN44-00424A

Also, I'm unable to determine if the TV is on or off. All I have to go by is the Power On lights that blinks when the AC cord is plugged in. I've tried to use the remote and the touch capacitance controls on the TV, but nothing changes with the Power On light, it just blinks away.

[budm]

Re: How to troubleshoot a BN44-00424A

The exposed pins that you can see and access from the top side of the board are the ODD number pins (you can see the number of the pins printed right next to the pins, I.E. 1, 3, 5, 7...), the EVEN number pins you will have to flip the board over or use the skinny probe to get to the connection where the wires enter the connector.

[Vista20]

Re: How to troubleshoot a BN44-00424A

Okay, thank you, I'll give that a try tonight.

[Vista20]

Re: How to troubleshoot a BN44-00424A

Okay, looking inside the pin socket on the PSU I see the EVEN row of pins. I checked these with the main board unplugged. Not sure the status of the TV, whether ON or OFF.

Pin 2 N.C 0v
Pin 4 EPWM 3.1v cycling, not constant
Pin 6 N.C 0v
Pin 8 BLU ON 3v cycling, not constant
Pin10 GND 0v
Pin 12 GND 0v
Pin 14 A5V 5.3v STEADY
Pin 16 PS-ON 1.48v cycling, not constant

Pin 1 N.C 0v
Pin 3 B13V 11.89v cycling, not constant
Pin 5 B13V 0v
Pin 7 V amp 0v
Pin 9 V amp 0v
Pin 11 GND 0v
Pin 13 B5V 0v
Pin 15 B5V 0v

Plugged the Main Board Connector into the PSU. All the voltages as shown in my earlier record are there, the 12.7v, the 18.9v and the 5.33v on the ODD pins, but cycling, not constant.

I checked the two 450V 68uf capacitors and they read ~393v, the other 450v 22uf reads ~370v.

[budm]

Re: How to troubleshoot a BN44-00424A

So with all the boards plugged in, how much is the is the variation on PIN 4 (EPWM), PIN 8 (BL-ON), and pin 16 (PS-ON)? A Couple Volts jumping up and down?

[budm]

Re: How to troubleshoot a BN44-00424A

It looks to me that your power supply is OK.
The LED strings are connected in series to form one large string, you need to leave the black probe on the chassis, then leave red probe on the L+ (the anode pin of the LED string) then turn on the TV to see how high the Voltage goes up to before settling down after 10 seconds, then turn the TV off and move the red probe to the L- and turn the TV on and see how high the Voltage goes up to before settling down after 10 seconds.
I will not be surprised if you have bad LEDs.
BTW, this power supply is also know for poor solder joints on the transformer legs, and on the legs of the devices attached to the heatsinks.

[budm]

Re: How to troubleshoot a BN44-00424A

I jsut notice this after looking to see what that cap is for:
"the other 450v 22uf reads ~370v"
That means you have open circuit in the LED connection some where.
It is supposed to be 330VDC with load.

[Vista20]

Re: How to troubleshoot a BN44-00424A

To check the voltage on the EVEN pins I'll have to unscrew the PSU and turn the board over. This will be hard to do with the LEDs plugged in.

So, if the LED is one large series string, wouldn't one burned LED prevent the rest from lighting? Also, I have a LED TV Backlight Tester GJ2C. I was able to see the backlight through the chassis holes when using this tester. I unplugged the LEDs and, using the tester, the LEDs can be seen lighting through the holes in the chassis.

[Vista20]

Re: How to troubleshoot a BN44-00424A

Okay, I think I'm going to disassemble the TV in the next few days. Based on other posts regarding this model, replacement LEDs are hard to find.

[budm]

Re: How to troubleshoot a BN44-00424A

You should test the SC Voltage at the L- return pin with all the cable in place to see if it shows any Voltage at all. You have 370VDC feeding the LED string (LED are connected in series) so it should have Voltage showing on the return pin as shown in my picture.
How did you connected the tester to test the LED string, you need to test ALL the strings and since they are terminated at the circuit board to form ONE the LED stgring so you will have to test each string correctly. Look at the picture I provide that shows how the LEDs are connected.
You have 4 wires from the LED assembly for two sets of LED strings, so how did you figure out which set of the LED string that you tested?
It is just like Christmas lights, one goes open circuit then the whole string will not light up. It sounds like you only test one set of LED.

[Vista20]

Re: How to troubleshoot a BN44-00424A

budm,
I tested the LEDs with the GJ2C by unplugging the backlight connection and with the red probe into #1 VF+ and the black probe into #3 (-), and the LEDs were visible through the chassis holes. Then I moved the red probe to #5 (+), and no lights.

Later today, when I get back home, I'll remove the PSU from the chassis, leaving all connections in place, and flip it over. I'll hook a jumper, with alligator clips, to the chassis and the board where one of the screws would be. This should ground the board, right?

Then I'll take voltage readings at the points you marked in your photo.
Thanks again for your help, I really appreciate it.

[budm]

Re: How to troubleshoot a BN44-00424A

https://www.badcaps.net/forum/attach...1&d=1509479270
No need to look at the board at this point, you have two pairs of wires for two set of LED string, each string has Black wire and Blue wire, so all you have to do is to disconnect LED connector from the power supply board and than use the LED tester to test each pair of wires, you should see backlights when you test each pair.

[Vista20]

Re: How to troubleshoot a BN44-00424A

budm,
Thanks, it looks like I've got some more work to do disassembling the TV. Then I'll grapple with repairing or replacing the LED strips. I've read that sourcing these particular LED strips is a problem.
I really appreciate your help.